1. Field of the Invention
This invention relates in general to an ethanol production process, and more particularly to methods of producing ethanol and whole stillage from a carbohydrate containing feedstock, such as corn, with and without a soy based feedstock, such as soybeans, and subsequent treatments of the whole stillage to produce recoverable value-added products.
2. Prior Art
With the ever-increasing depletion of economically recoverable petroleum reserves, as well as the environmental impact of the drilling processes to effect the recovery, the production of ethanol from carbohydrate containing sources as a partial or complete replacement for conventional fossil-based liquid fuels has become more attractive. A variety of materials have been utilized as the starch or sugar-containing feedstock in ethanol producing processes. One of the most common feedstock is whole corn kernels. In a conventional ethanol production process utilizing corn as the initial feedstock, the corn is first ground to produce a milled corn. This is typically achieved by the use of a hammer mill or other similar conventional milling equipment. Water, nutrients, and enzymes are then added to the milled corn to form a liquefied slurry. The liquefied slurry is then mixed in a fermentation vessel with water, yeast, and selected minerals and nutrients, whereby it then undergoes fermentation. The fermented product, commonly referred to as the “beer” is then distilled to produce an ethanol rich stream (about 95% ethanol and 5% water by weight) and a whole stillage, comprising water, as well as the solids resulting from the fermentation, from which by-products are then recoverable. Unfortunately, the by-products obtained from the conventional ethanol producing processes do not have sufficient economic value because of their relative low nutrient content to permit these processes from economically competing with conventional fossil fuel processes. Furthermore, because of the economics involved in the current process, the costs of producing ethanol and other resultant by-products has remained relatively high when compared to the fossil fuel sources, and such ethanol production processes have remained economically viable due mostly to government subsidies. Efforts to improve the economic viability of these processes have been addressed, but there still remains demand for the gain of further economic benefit from the use of an ethanol production process. Further improvements to the ethanol producing process that can either achieve processing cost savings or enhanced value by-products are therefore desirable.